Contrasting Historical and Physical Perspectives in Asymmetric Catalysis: ΔΔG versus Enantiomeric Excess.

With the rise of machine learning (ML), the modeling of chemical systems has reached a new era and has the potential to revolutionize how we understand and predict chemical reactions. Here, we probe the historic dependence on utilizing enantiomeric excess (ee) as a target variable and discuss the benefits of using relative Gibbs free activation energies (ΔΔG), grounded firmly in transition-state theory, emphasizing practical benefits for chemists. This perspective is intended to discuss best practices that enhance modeling efforts especially for chemists with an experimental background in asymmetric catalysis that wish to explore modelling of their data.

Ultrafast energy-dispersive soft-x-ray diffraction in the water window with a laser-driven source.

Time-resolved soft-x-ray-diffraction experiments give access to microscopic processes in a broad range of solid-state materials by probing ultrafast dynamics of ordering phenomena. While laboratory-based high-harmonic generation (HHG) light sources provide the required photon energies, their limited photon flux is distributed over a wide spectral range, rendering typical monochromatic diffraction schemes challenging. Here, we present a scheme for energy-dispersive soft-x-ray diffraction with femtosecond temporal resolution and photon energies across the water window from 200 to 600 eV.

Perfluoroalkyl acid precursor or weakly fluorinated organic compound? A proof of concept for oxidative fractionation of PFAS and organofluorines.

Organofluorine mass balance approaches are increasingly applied to investigate the occurrence of per- and polyfluoroalkyl substances (PFAS) and other organofluorines in environmental samples more comprehensively. Usually, complex samples prevent the identification and quantification of every fluorine-containing molecule. Consequently, large unidentified fractions between fluorine sum parameters such as extractable organic fluorine (EOF) and the sum of quantified analytes are frequently reported.

A bis-Phenolate Carbene-Supported bis-μ-Oxo Iron(IV/IV) Complex with a [Fe(μ-O)Fe] Diamond Core Derived from Dioxygen Activation.

The diiron(II) complex, [(OCO)Fe(MeCN)] (, MeCN = acetonitrile), supported by the bis-phenolate carbene pincer ligand, 1,3-bis(3,5-di--butyl-2-hydroxyphenyl)benzimidazolin-2-ylidene (OCO), was synthesized and characterized by single-crystal X-ray diffraction, H nuclear magnetic resonance, infrared (IR) vibrational, ultraviolet/visible/near-infrared (UV/vis/NIR) electronic absorption, Fe Mössbauer, X-band electron paramagnetic resonance (EPR) and SQUID magnetization measurements. Complex activates dioxygen to yield the diferric, μ-oxo-bridged complex [(OCO)Fe(py)(μ-O)Fe(O(C═O)O)(py)] () that was isolated and fully characterized. In , one of the iron-carbene bonds was oxidized to give a urea motif, resulting in an O(C═O)O binding site, while the other Fe(OCO) unit remained unchanged.

Detection of Tn-antigen in breast and prostate cancer models by VVL-labeled red dye-doped nanoparticles.

Fluorescence detection of breast and prostate cancer cells expressing Tn-antigen, a tumor marker, with lectin (VVL)-labeled nanoparticles. Breast and prostate cancer cells engineered to express high levels of Tn-antigen and non-engineered controls were incubated with VVL-labeled or unlabeled red dye-doped silica-coated polystyrene nanoparticles. The binding to cells was studied with flow cytometry, confocal microscopy, and electron microscopy.

UV-vis absorbance spectra, molar extinction coefficients and circular dichroism spectra for the two cyanobacterial metabolites anabaenopeptin A and anabaenopeptin B.

The UV-vis absorbance spectra, molar extinction coefficients and circular dichroism spectra, as well as NMR and high resolution tandem mass spectrometry spectra were determined for two prominent secondary metabolites from cyanobacteria, namely anabaenopeptin A and anabaenopeptin B. The compounds were extracted from the cyanobacterium CBT929 and purified by flash chromatography and HPLC. Exact amounts of isolated compounds were assessed by quantitative H-NMR with internal calibrant ethyl 4-(dimethylamino)benzoate in DMSO‑ at 298 K with a recycle delay (d1) of 120 s.

Shrimp-shaped structure and period-bubbling route to chaos in a one-dimensional economic model.

A beautiful feature of nature is its complexity. The chaos theory has proved useful in a variety of fields, including physics, chemistry, biology, and economics. In the present article, we explore the complex dynamics of a rather simple one-dimensional economic model in a parameter plane.

New Processes for Ionizing Nonvolatile Compounds in Mass Spectrometry: The Road of Discovery to Current State-of-the-Art.

This covers discovery and mechanistic aspects as well as initial applications of novel ionization processes for use in mass spectrometry that guided us in a series of subsequent discoveries, instrument developments, and commercialization. matrix-assisted ionization on an intermediate pressure matrix-assisted laser desorption/ionization source the use of a laser, high voltages, or any other added energy was simply unbelievable, at first. Individually and as a whole, the various discoveries and inventions started to paint, , an exciting new picture and outlook in mass spectrometry from which key developments grew that were at the time unimaginable, and continue to surprise us in its simplistic preeminence.

From Ions to Crystals: A Comprehensive View of the Non-Classical Nucleation of Calcium Sulfate.

The early stages of mineralization continue to be in the focus of intensive research due to their inherent importance for natural and engineered environments. While numerous observations have been reported for single steps in the pathways of various crystallizing phases in previous studies, the complexity of the underlying processes and their elusive character have left central questions unanswered in most cases. In the present work, we provide a detailed view on the nucleation of calcium sulfate mineralization-an abundant mineral with broad use in construction industry-in aqueous systems at ambient conditions.

Switchable protection and exposure of a sensitive squaraine dye within a redox active rotaxane.

In nature, molecular environments in proteins can sterically protect and stabilize reactive species such as organic radicals through non-covalent interactions. Here, we report a near-infrared fluorescent rotaxane in which the stabilization of a chemically labile squaraine fluorophore by the coordination of a tetralactam macrocycle can be controlled chemically and electrochemically. The rotaxane can be switched between two co-conformations in which the wheel either stabilizes or exposes the fluorophore.

Unraveling chemical origins of dendrite formation in zinc-ion batteries via in situ/operando X-ray spectroscopy and imaging.

To prevent zinc (Zn) dendrite formation and improve electrochemical stability, it is essential to understand Zn dendrite growth, particularly in terms of morphology and relation with the solid electrolyte interface (SEI) film. In this study, we employ in-situ scanning transmission X-ray microscopy (STXM) and spectro-ptychography to monitor the morphology evolution of Zn dendrites and to identify their chemical composition and distribution on the Zn surface during the stripping/plating progress. Our findings reveal that in 50 mM ZnSO, the initiation of moss/whisker dendrites is chemically controlled, while their continued growth over extended cycles is kinetically governed.

The fluctuation-dissipation relation holds for a macroscopic tracer in an active bath.

The fluctuation-dissipation relation (FDR) links thermal fluctuations and dissipation at thermal equilibrium through temperature. Extending it beyond equilibrium conditions in pursuit of broadening thermodynamics is often feasible, albeit with system-dependent specific conditions. We demonstrate experimentally that a generalized FDR holds for a harmonically trapped tracer colliding with self-propelled walkers.

Characterization of Anticancer Drug Protomers Using Electrospray Ionization and Ion Mobility Spectrometry-Mass Spectrometry.

We used electrospray ionization and ion mobility spectrometry-mass spectrometry to detect and characterize the three anticancer drugs palbociclib, copanlisib, and olaparib. Ion mobility-mass spectrometry and density functional theory revealed that these compounds generate isomers during ionization (protomers) due to the presence of multiple protonation sites within their chemical structures. Our work has implications for understanding the solution- and gas-phase chemistry of these molecules during spray-based ionization processes.

The role of temperature in the photoluminescence quantum yield (PLQY) of AgS-based nanocrystals.

Highly emissive AgS nanocrystals (NCs) passivated with a gradated shell incorporating Se and Zn were synthesized in air, and the temperature dependence of their photoluminescence quantum yield (PLQY) was quantified in both organic and aqueous media at ∼1200 nm. The relevance of this parameter, measured at physiological temperatures, is highlighted for applications that rely on the near infrared (NIR) photoluminescence of NCs, such as deep NIR imaging or luminescence nanothermometry. Hyperspectral NIR imaging shows that AgS-based NCs with a PLQY in organic media of about 10% are inefficient for imaging at 40 °C through 20 mm thick tissue with low laser irradiation power densities.

High-repetition-rate ultrafast electron diffraction with direct electron detection.

Ultrafast electron diffraction (UED) instruments typically operate at kHz or lower repetition rates and rely on indirect detection of electrons. However, these experiments encounter limitations because they are required to use electron beams containing a relatively large number of electrons (≫100 electrons/pulse), leading to severe space-charge effects. Consequently, electron pulses with long durations and large transverse diameters are used to interrogate the sample.

Flexible Wearable Tri-notched UWB Antenna Printed with Silver Conductive Materials.

The advancement of Internet of Things and associated technologies has led to the widespread usage of smart wearable devices, greatly boosting the demand for flexible antennas, which are critical electromagnetic components in such devices. Additive manufacturing technologies provide a feasible solution for the creation of wearable and flexible antennas. However, performance reliability under deformation and radiation safety near the human body are two issues that need to be solved for such antennas.

Compact Electron Paramagnetic Resonance on a Chip Spectrometer Using a Single Sided Permanent Magnet.

Electron paramagnetic resonance (EPR) spectroscopy provides information about the physical and chemical properties of materials by detecting paramagnetic states. Conventional EPR measurements are performed in high resonator using large electromagnets which limits the available space for operando experiments. Here we present a solution toward a portable EPR sensor based on the combination of the EPR-on-a-Chip (EPRoC) and a single-sided permanent magnet.

Structure and Dynamics of ATP and the ATP-Zn Complex in Solution.

Despite the crucial role of ATP in life and artificial life-like applications, fundamental aspects relevant to its function, such as its conformational properties and its interaction with water and ions, remain unclear. Here, by integrating linear and two-dimensional infrared spectroscopy with molecular dynamics, we provide a detailed characterization of the vibrational spectra of the phosphate groups in ATP and in its complex with Zn in water. Our study highlights the role of conformational disorder and solvation dynamics, beyond the harmonic normal-mode analysis, and reveals a complex scenario in which electronic and environmental effects tune the coupling between phosphate vibrations.

Attosecond impulsive stimulated X-ray Raman scattering in liquid water.

We report the measurement of impulsive stimulated x-ray Raman scattering in neutral liquid water. An attosecond pulse drives the excitations of an electronic wavepacket in water molecules. The process comprises two steps: a transition to core-excited states near the oxygen atoms accompanied by transition to valence-excited states.

Steerable current-driven emission of spin waves in magnetic vortex pairs.

The efficient excitation of spin waves is a key challenge in the realization of magnonic devices. We demonstrate current-driven generation of spin waves in antiferromagnetically coupled magnetic vortices. We use time-resolved x-ray microscopy to directly image the emission of spin waves upon the application of alternating currents flowing directly through the magnetic stack.

How big is big data?

Big data has ushered in a new wave of predictive power using machine-learning models. In this work, we assess what big means in the context of typical materials-science machine-learning problems. This concerns not only data volume, but also data quality and veracity as much as infrastructure issues.

Nanohoops in membranes: confined supramolecular spaces within phospholipid bilayer membranes.

Nanohoops, an exciting class of fluorophores with supramolecular binding abilities, have the potential to become innovative tools within biological imaging and sensing. Given the biological importance of cell membranes, incorporation of macrocyclic materials with the dual capability of fluorescence emission and supramolecular complexation would be particularly interesting. A series of different-sized nanohoops-ethylene glycol-decorated []cyclo--pyrenylenes (CPYs) ( = 4-8)-were synthesised an alternate synthetic route which implements a stannylation-based precursor, producing purer material than the previous borylation approach, enabling the growth of single-crystals of the Pt-macrocycle.

Spin Dynamics across Metallic Layers on the Few-Femtosecond Timescale.

We measure the light-driven response of a magnetic multilayer structure made of thin alternating layers of cobalt and platinum at the few-femtosecond timescale. Using attosecond magnetic circular dichroism, we observe how light rearranges the magnetic moment during and after excitation. The results reveal a sub-5 fs spike of magnetization in the platinum layer, which follows the shape of the driving pulse.